This invention relates generally to load responsive bypass flow control of a fixed displacement pump, which automatically maintains pump discharge pressure higher, by a constant pressure differential, than the load pressure signal transmitted from system control valves.
In more particular aspects this invention relates to bypass flow control of a fixed displacement pump, which is controlled by a pilot valve responsive to load pressure signals transmitted from system control valves.
In still more particular aspects this invention relates to an unloading control of load responsive bypass flow control of a fixed displacement pump, which in absence of load pressure signal permits the load responsive bypass flow control to bypass pump flow to system reservoir at a minimum pressure level, lower than the constant pressure differential of load responsive bypass flow control.
During control of positive load the load responsive bypass flow control of a fixed displacement pump automatically maintains a constant pressure differential between the pump discharge pressure and the load pressure. Depending on the type of control and on the required response characteristics this constant pressure differential may be quite high. Since during standby condition the load responsive bypass flow control will maintain the system pressure at a level equal to the constant pressure differential of the control, the standby horsepower loss can be quite high.